Abstract
We investigated the effect of supports based on ZrO2, TiO2, Al2O3, and SiO2 on the rate of propene formation in the metathesis of ethylene with 2-butene at 50 °C over Mo-containing catalysts possessing highly dispersed MoOx. Large improvements in this rate were achieved when using supports composed of mixed oxides (ZrO2–SiO2, ZrO2–PO4, TiO2–SiO2; Al2O3–SiO2) rather than of individual oxides (ZrO2, TiO2, Al2O3, SiO2). Although previous literature studies dealing with the metathesis reaction over Al2O3- or SiO2-suppported catalysts at higher temperatures suggest the importance of redox or acidic properties of supported MoOx species for catalyst activity, we were not able to establish any general direct correlation in this regard. Contrarily, the rate of propene formation can be significantly enhanced when promoting supports with an oxide promoter. We suggest that the created support lattice defects may facilitate the transformation of MoOx to Mo carbenes under reaction conditions or improve the intrinsic activity of the latter.Graphic
Highlights
Metathesis of ethylene with 2-butene is one of the industrial processes for on-purpose production of propene [1]
Mo supported on SiO2, Al2O3, or S iO2–Al2O3 [2]. WOx/ SiO2 applied on the large scale is characterized by low price, long lifetime, and resistance to poisoning [3,4,5]. WOx-based catalysts are, active at relatively high temperatures (∼350–450 °C), while MoOx- or ReOx-based catalysts demonstrate high activity at lower temperatures (25–200 °C) [2, 6]
[17] The influence of co-catalysts such as CaO, Al2O3 or SiO2–Al2O3 on the metathesis of ethylene and 2-butene to propene over MoOx/AlxSiyOz was investigated by Goelden et al [8]
Summary
Metathesis of ethylene with 2-butene is one of the industrial processes for on-purpose production of propene [1]. It was important to check if the general activity-governing relationships established for the often-tested catalysts are relevant for the-above-mentioned alternatives and at 50 °C To this end, we prepared a series of Mo-containing catalysts possessing highly dispersed M oOx species on the surface of TiO2- or ZrO2-based supports as well as of SiO2, Al2O3 and SiO2–Al2O3. We prepared a series of Mo-containing catalysts possessing highly dispersed M oOx species on the surface of TiO2- or ZrO2-based supports as well as of SiO2, Al2O3 and SiO2–Al2O3 They were tested for their activity in the metathesis of ethylene with 2-butene and characterized by complementary state-of-the-art techniques
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